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该文对微量排气阀的原理进行了介绍,并对微量排气阀的口径和安装位置选择进行了阐述。最后,通过工程实例证明了微量排气阀对长距离输水管线的安全运行起到重要的作用。 相似文献
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煤矿矿区铁路集配站位置的选择 总被引:2,自引:1,他引:1
余静 《辽宁工程技术大学学报(自然科学版)》1999,18(6):574-578
在分析煤矿矿区铁路运输系统的结构特点及货流特点的基础上,采用优化理论和数学中求极值的思想,以换算运营费最小为目标,进行了煤矿铁路运输系统集配站位置的研究,给出了既有运输系统及新建运输系统铁路集配站位置的选择方法。 相似文献
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停车换乘站位置选择及换乘需求预测 总被引:11,自引:0,他引:11
城市中心区外相邻轨道站处的停车换乘站位置选择是城市停车换乘规划中经常遇到的问题,但目前尚没有简单、操作性较强的解决方法。对此,首先给出换乘站位置选择时应遵循的原则,然后在分析这些原则的基础上,给出停车换乘站位置选择的方法及程序,并且对这一方法进行了一般性推广。探讨了停车换乘站换乘需求预测的方法,给出了预测时所需资料的调查内容、调查方法,以及换乘需求量计算的主要参数和自变量的确定方法。实例表明,该方法具有很强的可操作性。 相似文献
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基于位置的服务(location based services, LBS)为人们日常生活带来极大便利的同时也严重地威胁到用户的隐私.为了在保护用户位置隐私的同时降低用户的查询代价,提出了一种基于安全索引的位置隐私保护方法(location privacy protection method based on secure index, LPPMSI).LPPMSI不需要用户搜集数据信息,数据拥有者为虚假位置信息建立安全索引.用户能够安全、快速地检索到虚假位置信息,服务器再执行基于虚假位置的LBS.并且还提出了基于滑动窗口的候选位置选择算法,有效减少候选位置选择时间.实验结果表明,LPPMSI在不改变隐私保护能力的前提下,不需要用户花费大量时间搜集数据分布及查询概率信息. 相似文献
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探索城市轨道交通乘客站台候车位置选择行为的影响因素,从乘客主体、站台特性、列车运行等3方面分析其对候车位置选择行为的影响。应用Logit模型,构建了包含拥挤容忍程度、排队长度、列车车厢满载率、走行距离、视野关注范围、出行目的等6个影响因素的乘客候车位置选择行为模型。通过调查问卷数据对模型参数进行标定。结果表明不同轨道交通乘客候车位置选择行为存在差异,拥挤容忍程度高的乘客倾向于综合列车车厢满载率和排队长度再选择候车位置,而视野关注范围小的乘客倾向于综合走行距离和列车车厢满载率再选择候车位置。 相似文献
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《湖南工程学院学报(自然科学版)》2015,(3)
为了探讨户外广告牌的结构安全评估方法,以高速公路两侧典型的非平行双面单立柱广告牌为例,利用CFD软件计算得到广告牌各部位在不同工况下的风压力,然后凭借有限元软件对公路广告牌进行结构分析,获得广告牌结构各构件的应力和位移,并对各工况条件下广告牌结构的损伤情况进行了评估.结果表明,风向角为30°时对公路广告牌结构的安全最为不利,同时发现,与面板相连的广告牌支架的应力和位移始终较大,在风荷载下容易屈服或因变形过大而导致面板脱落,在设计中应予以重视.该研究方法可用于高速公路广告牌结构的精细计算和损伤评估. 相似文献
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胡光华 《国外科技新书评介》2008,(11)
自主移动机器人学是一个涉及技术和科学范畴的令人神往的研究领域,而其中的崎岖地形机器人学则是一个快速演变的研究范畴,人们在实现户外车辆极大程度上的自主方面投入了大量的努力。本书把漫游者在崎岖地形运动考虑成为一个整体的问题,并以此来改进示范三维位置跟踪的准确性。除了选择合适的传感器之外,在机械结构加上使用有限的车轮滑行为跨越障碍物的平稳运动创造了条件。 相似文献
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地下工程开挖以前,必须了解原岩应力,为岩体工程设计提供科学的理论依据,选择正确的硐室位置,以最大限度地提高成形硐室的稳定性,对工程设计具有十分重要的意义。 相似文献
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Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness. 相似文献
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Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly. 相似文献
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理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。 相似文献
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As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death. 相似文献
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Miao Maosheng 《华南师范大学学报(自然科学版)》2014,(6)
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula- 相似文献
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Yang Weitao 《华南师范大学学报(自然科学版)》2014,46(6):137-138
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re- 相似文献
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Bernard Kirtman 《华南师范大学学报(自然科学版)》2014,(6)
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that 相似文献
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《上海师范大学学报(自然科学版)》2014,(5):550
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with 相似文献
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《吉林大学学报(理学版)》2014,(5):1105
<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has 相似文献